Modify ComboBox size adding Styles css class

[zcittadin]

Hello.
I have created a form with some TextFields, Buttons and a ComboBox.
I would like to use Styles.SMALL to modify the size of the controls.
This works with TextField and Button, but not with ComboBox.
Is there any other way to achieve this?
I tried: combo.getStyleClass().addAll(Styles.SMALL);
But without success.